As of October 2009, over 500 WiMAX (fixed and mobile) networks have been deployed in over 145 countries. The WiMAX (Worldwide Interoperability for Microwave Access) technology is one that is based on the IEEE 802.16 Standard which keeps evolving as the demand for high speed data services for mobile users, increases. As a result, many of the deployed networks are being upgraded to cater this demand. For example, networks that are based on one of the early technologies utilizing IEEE 802.16e Standard, known as Mobile-WiMax, are being upgraded to comply with IEEE 802.16 m Standard. The Base Stations in the upgraded or enhanced networks are known as Advanced Base Stations (ABSs) that are capable of supporting both IEEE 802.16e Standard based traffic as well as IEEE 802.16 m Standard based traffic, while upgraded Mobile Subscribers are accordingly known as Advanced Mobile Subscribers (AMSs).
In the IEEE 802.16 m framework there are certain broadcast messages named as Advanced MAP Information Elements (A-MAP IEs) that contain aggregated multi unicast information addressed for one or multiple users. In order to efficiently provide control information WO 09112928 teaches the use of a broadcast pointer channel (BPCH) to identify the type and perhaps relative location of control information that is being provided in a given frame structure, such as a sub-frame, frame, or superframe. A sub-frame has a BPCH and a corresponding system control information segment in which control information resides. The system control information segment has a number of control information blocks, wherein each control information block that is present corresponds to a particular type of control information. The BPCH is used to identify the type of control information that is present in a corresponding system control information segment, and if needed or desired, the relative locations of the various control information.
Another example of such broadcast messages that contain aggregated multi unicast information for multiple users, is the BR-ACK MAP-IE message that is used when the ABS receives Bandwidth Request (BR) sequences sent by one or more AMSs. The ABS then sends the BR-ACK A-MAP IE in the next frame, containing acknowledgment and optionally bandwidth grants for the requesting AMSs. In spite of the advantages associated with this technique of sending aggregated multi unicast information in broadcast messages, it also has some drawbacks, for example the inefficiency caused by the fact the message should be sent at the lowest Modulation and Coding Scheme (MCS) that is expected to be decoded by all addressed users. When broadcasting a single A-MAP IE message with aggregated multi unicast information to multiple users (in our example, to acknowledge the BRs received from multiple users), it is found to a rather wasteful process and may lead to significant A-MAP controlling overhead.
The present invention seeks to provide an efficient solution for the problem of broadcasting aggregated multi unicast information to multiple users having different MCS capabilities.